The orb is spinning out from your character and the blizzard is coming from above. Blizzard is better in some cases, in others orb is better.
It very much depends on the build you're using:
-any other attacks or just pure blizzard or pure orb?
-other skill point distribution?
-what's your budget?
-what do you want to achieve with the build?
If you want people to take time to discuss your topic, you might want to put some effort in it yourself.
I prefer blizzard: it's more powerful, more surprising (falls from the sky), less absorbable and 1-shot-kills are very possible.
However, I agree with LorveN: people would need more details to give you a better answer. My personnal answer was based on the following: you are rich enough to afford perfect equipment and you are looking to make a softcore pvp char.
Personally I tend to prefer Frozen Orb. Although Blizzard's damage is potentially higher, it's also more inconsistent in how often it hits. With good targeting you can make FO do a lot of damage each time you cast it.